Musical instrument employing film sound track on cathode ray tube screen



Dec. 16. 21969 R. E. RUPERT MUSICAL INSTRUMENT EMPLOYING FILM SOUNDTRACK ON CATHODE RAY TUBE SCREEN Filed April 26, 1966 2 Sheets-Sheet 1PRE AMPLIFIER CIRCUIT LOW FREQUENCY MODULATION DETECTOR VOLUME LEVELSENSING CIRCUIT VERT|CAL VERTICAL DRIVER CIRCUIT CONVERTQR HORIZONTALEFLECTION C'RCUIT CIRCUIT DEFLECTION OSCILLATOR C|RCU|T HIGH VOLTAGEPOWER SUPPLY CIRCUIT SWITCHING CIRCUIT HORIZONTAL DEFLECTION CIRCUITVERT ICAL AMPLIFIER CIRCUIT LOUD SPEAKER DEFLECTION CIRCUIT VERTICAL'OSCILLATOR CIRCUIT F IG. 2

CATHODE TUBE AMPLIFIER LOUD CIRCUIT SPEAKER INVENTOR ROBERT E. RUPERTwmflmk 092;:

ATTORNEY R. E. RUPERT 3,484,530 MUSICAL INSTRUMENT EMPLOYING FILM SOUNDTRACK Dec. 16. 1969 ON CATHODE RAY TUBE SCREEN 2 Sheets- Sheet 2 FiledApril 26, 1966 .EDOEO .EDOwtU mmvawmw D304 .IDOEG mwwwrmk .EDOEOmokikzmmmmhrn ZOFQMTEMO .EDOmzO FBOEQ 0262mm MEDJO United States Patent3,484,530 MUSICAL INSTRUMENT EMPLOYING FILM SOUND TRACK ()N CATHODE RAYTUBE SCREEN Robert E. Rupert, 60 Whittier Road, Wakefield, Mass. 01880Filed Apr. 26, 1966, Ser. No. 545,463 Int. Cl. Gh 3/06, 3/04 U.S. Cl.84-1.18 8 Claims ABSTRACT OF THE DISCLOSURE This invention relates toelectro-optic apparatus for producing musical tones accuratelysimulating the tones of a selected musical instrument such as aconventional brass, woodwind or stringed instrument. According to theinvention, a cathode ray tube with a short persistency screen phosphoris used in conjunction with a film sound track to provide a varyingelectric current to be fed into a loud speaker for the production oftones characteristic of the selected musical instrument.

Various means may be employed to energize the cathode ray tube, threesuch means being illustrated in the drawings, of which:

FIG. 1 is a diagrammatic layout of apparatus for producing musical tonesin response to a vocal input;

FIG. 2 is a diagrammatic layout of apparatus constituting a musicalinstrument to be played by striking keys like those of a piano;

FIG. 3 is a diagrammatic layout of a modification of the invention, and,

FIG. 4 is a view in front elevation of a series of variable areaoptically recorded sound tracks applied to the face of a cathode raytube.

In FIG. 1 are illustrated several conventional electronic circuitscoupled to a relatively simple electro-optic assembly that reproducesoptically recorded musical instrument notes. The reproduced notes arestimulated by vocal sounds fed to the audio input circuits by a contacttype microphone.

Because a full range of notes on the musical scale can be reproduced instep with the vocal signals applied, this device constitutes a playablemusical instrument like any conventional brass, woodwind or stringinstrument, but is far simpler to play since only the vocal cords andrelated muscles are involved.

True reproduction of instrumental tones is further enhanced by detectingthe low frequency modulation and changing volume of each note as theyare fed to the circuits and applying these effects to the deliveredrecorded musical note. The function of each of the circuits is asfollows:

A microphone 12 receiving vocal sound waves from the player passes asignal current to the audio pre-amphfier circuit 13. The audiopro-amplifier circuit 13 amplifies the microphone signal currents andpasses them to the driver circuit 14 where suflicient power build-up ofthe signal occurs to operate the frequency-to-DC. convertor circuit 15.The frequency-to-DC. convertor circuit will produce an output voltagethat is proportional to the fundamental frequency applied. Since thefundamental in most complex waveforms has the highest amplitude of3,484,530 Patented Dec. 16, 1969 all its components, part of thefrequency-to-D.C. convertor circuit is able to hold the signal levelconstant, similar to an automatic volume control circuit, so that thepeaks will be available for detection and counting. The frequency-to-DC.conversion voltage is then applied to a horizontal deflection circuit 16to drive an electron beam 3 horizontally in the electrostatic cathoderay tube 1. Each note on the chromatic scale can be represented by ahorizontal position on the phosphor screen face of the cathode ray tube.At each horizontal position on the face of the cathode ray tube 1 isattached a section of photographic film sound track 4 similar to thatused in motion picture projection, the sound track being a recording ofnotes from the selected musical instrument. The electron beam 3 thuswill produce a spot 18 of light behind each film section. A scanningmotion of the beam is caused by having the beam 3 deflected verticallyby appropriate voltages on the cathode ray tube vertical deflectionplates. These voltages are generated in the vertical oscillator circuit10 and the vertical deflection circuit 11. The vertical oscillatorfrequency is set so that the scanning rate of the light spot on thecathode ray tube will produce a signal into the optical system thatgives the proper musical pitch, the light beam having been modulated bythe film sound track in its path. The vertical deflection voltagegenerated in the vertical deflection circuit 11 and whose frequency iscontrolled by the vertical oscillator 16, has a sawtooth or ramp waveform which results in the beam moving uniformly in the verticaldirection at a rate depending on the slope of the ramp, and returningrapidly to its starting point when the trailing edge of the wave passes.The trailing edge of the waveform produces the return trace; this may beeliminated by insertion of a blanking circuit. The circuits describedhere are commonly found in todays modern television receivers. Modulatedlight rays 5 emanating from the film sound track are collected by thelight collector 6 which may be a concave mirror, and are reflected andfocused on the light sensor 8. This transducer responds to the visiblelight energy emitted by the screen phosphor 2 and generates signalcurrents which are amplified in circuit 9 and then passed on to the loudspeaker system 19. Low frequency modulation of the generated musicaltone is accomplished by separating this frequency from the input signalin circuit 17, the low frequency modulation detector, and applying theresulting signal to the cathode of the cathode ray tube and the electronbeam in turn. Loudness or volume of the signal current is detected in avolume level sensing circuit 21 and also is superimposed on the cathodepotential of the cathode ray tube circuit where it influences the beamintensity and the resulting light spot behind the film sound track. Eachelectronic circuit in FIG. 1 is assumed to have its power supplied. Ahigh voltage power supply circuit 18 has been added separately for thecathode ray tube. Thus by the use of such apparatus a vocal melody istransformed into an instrumental melody.

In the apparatus diagrammatically illustrated in FIG. 2, a film soundtrack 4 is employed in conjunction with a cathode ray tube 1, a sensor 8and a loud speaker 19. The parts of the apparatus employed to energizethe tube, however, are arranged to be played like a piano with a set ofkeys, one such key 22 being illustrated by way of example. When the keyis depressed, the switching circuit 24 is activated and causes apotential to change in the cathode ray tube which turns on the electronbeam. The electron beam 3 excites the phosphor screen 2 on the face ofthe cathode ray tube and emits visible light energy. The light energy soemitted is caused to pass through a. section of photographic film soundtrack 4 that has been attached to the front of the cathode ray tube. Theoptically recorded sound information contained on the film sound trackmodulates the light passing through it as light of varying intensity.The switching circuit 24 also energizes the horizontal deflectioncircuit 16 causing a predetermined amount of deflection voltage toappear on the horizontal deflection plates within the tube whichpositions the spot on an appropriate film sound track section. Scanningof the section of film sound track is accomplished by moving the beamvertically over the track by applying appropriate voltages to thevertical deflection plates of the cathode ray tube. These voltages aregenerated in the vertical deflection circuit 11 and frequency controlledby the oscillations produced in the vertical oscillator circuit 10. Thevertical deflection voltage applied to the vertical deflection plates ofthe cathode ray tube has a sawtooth or ramp waveform which results inthe beam moving uniformly in the vertical direction at a rate dependingon the slope of the ramp and returning rapidly to its starting pointwhen the trailing edge of the wave passes. The trailing edge of thewaveform produces the return trace; this may be eliminated by insertionof a blanking circuit. The circuits described here are commonly found intodays modern television receivers.

The emerging light rays 5 are then gathered by the light energycollector 6. The light collector collects, reflects and focuses thelight rays on the light sensor 8. The focused rays 7 are shown. Lightrays falling on the light sensor induce electrical signal currents inthe light sensor circuit due to the modulating action of thephotographic film sound strip which is interposed between the phosphorscreen and the optical system. These currents are then further amplifiedin the amplifier circuit 9 coupled to the photocell 8. The amplifiedmusical tones are then heard over the loudspeaker system 19 attached tothe amplifier circuit 9.

To produce the several notes of a scale, a corresponding number ofparallel sound tracks are provided on the film 4, these tracks beingphoto recordings of notes of different pitch as played on the selectedinstrument. There is also a corresponding number of keys 22, each keybeing connected to the tube 1 through its own horizontal deflectorcircuit 16 by which the voltage transmitted to the tube is adjusted todirect and hold the electron beam 3 to the particular sound track on thefilm 4 which corresponds to the key 22 which is being depressed.

In the systems described and illustrated in FIGS. 1 and 2, one sectionof film sound track 4 is employed for each musical note that is to begenerated. Thus a number of different tracks are required to reproduce anumber of different musical notes. Three such different tracks 4a, 4band 4c are shown in FIG. 4. This arrangement requires means fordeflecting the electron beam to various predetermined horizontalpositions in order to scan each film strip representing a note. Analternate means of generating notes of different pitch by the use ofonly one strip of film sound track is illustrated in the modification ofFIG. 3.

In this embodiment a microphone 12 receiving vocal sound waves from theoperator passes the signal current to the audio preamplifier circuit 13.The audio pre-amplifier circuit 13 amplifies the microphone signalcurrents and passes them to thbe driver circuit 14 where the signaloverdrives an amplifying tube or transistor to produce a nearly squarewave form in the output. The square wave is then fed to a differentiatorcircuit 26 where the leading and trailing edges of the square wavesignal produce spikes or pulses of short duration. These pulses are thenfed to a trigger circuit 28 that responds only to either the leading orthe trailing edge pulses (positive going pulses or negative goingpulses, respectively). There will be one pulse of this sort for eachelectrical cycle of the fundamental in the vocal input signal. Thesepulses are now used to initiate and synchronously control the frequencyof oscillation in a multivibrator circuit 30. The square wave voltagesproduced here are then fed to a vertical deflection circuit 32 which hasbuilt into it a ramp generator that will produce a sawtootlrvoltage waveform of constant peak amplitude. While these waveforms are of constantamplitude they are characterized by ramps that vary in slope angle, orrate of buildup, the rate being determined and controlled by themultivibrator frequency by means of an integration network in the rampgenerator. These sawtooth waveforms, whose ramp angles vary withfrequency in step with the vocal input, are then used to deflect theelectron beam vertically by means of the vertical deflection circuit andto thereby cause the spot 18 to scan the film strip at varying rates andthus produce diflerent pitched notes. The film sound track in this casecontains several complete optically recorded cycles of the lowestpitched musical note, the exact numher being determined by the number ofoscillations required during integration to produce the peak rampvoltage. Since this arrangement requires only one film sound track toreproduce the sound of one musical instrument, additional space isavailable on the tube face for other sound track strips as suggested inFIG. 4 permitting several musical instruments to be reproduced in thesame system, each sound track being formed to reproduce the overtones ofthe instrument it represents. The player then selects the instrumentsound he wishes to reproduce by an instrument selector circuit 34 whichsupplies a predetermined amount of deflection voltage to the horizontaldeflection plates of the cathode ray tube for each selector position.This deflection voltage is fed through the horizontal deflection circuit16 to the direct and hold the electron beam onto the proper film stripwith the vertical scanning motion being applied as previously described.Low frequency modulation and volume techniques are utilized as describedand illustrated in FIG. 1.

While the invention has been described with particular reference to theillustrted embodiments, it will be understood that numerousmodifications thereto will appear to those skilled in the art. Forexample, the sounds of two or more instruments may be reproducedsimultaneously by the use of a cathode ray tube with a double (or more)beam and associated deflecting plates and circuitry. In such a case thetwo (or more) beams may be scanned over separate sound tracks, each of adifferent instrument and thereby reproduce the two sounds from a singleinput. As another modification, the concave mirror may be replaced by alens interposed between the tube and the transducer 8. Varioustransducing devices may be employed such as silicon detectors, photomultiplying tubes and the like. Obviously, the sound tracks may bearranged in a variety of positions on the tube face such as horizontallyor vertically, side by side or sections end to end with appropriatemodification of the control circuitry. The track itself may be of thevariable area or of the variable density type, as desired.

Accordingly, the above description and accompanying drawings should betaken as illustrative of the invention and not in a limiting sense.

Having thus described the invention, what I claim and desire to obtainby Letters Patent of the United States is:

1. Apparatus for producing musical tones accurately simulating tones ofa selected musical instrument, comprising a cathode ray tube having aphosphor screen, a film sound track on which are optically recorded inindividual areas, individual tones from said instrument, means forenergizing said tube to project an electron beam from the cathode to thescreen and to scan a portion of the screen, a light sensor, a lightcollector arranged to focus on said sensor the light rays emitted bysaid screen past said film, a loud speaker, means for amplifying thevariable current from the sensor to the loud speaker, and means ofcontrolling said energizing means to limit the scanning movements ofsaid electron beam to predetermined ones of said individual areas.

2. Apparatus as described in claim 1, said film having a series ofparallel sound tracks thereon for selective scanning by said electronbeam, said tracks corresponding respectively to a series of notes in amusical scale.

3. Apparatus as described in claim 2, said controlling means includingmeans operable to select the successive musical notes to be sounded bysaid loud speaker.

4. Apparatus as described in claim 3, said controlling means including ahorizontal deflector circuit for each of said parallel sound tracks anda switch key for each set of horizontal and vertical deflector circuits.

5. Apparatus as described in claim 2, said controlling means including amicrophone into which notes of dif-.,

ferent pitch may be successively sounded, a horizontal deflectioncircuit connected between said microphone and said cathode ray tube, avertical deflection circuit operatively connected to said tube, andelectrical means connected between said microphone and tube andresponsive to the fundamental pitch of a note sounded into saidmicrophone to limit the horizontal scanning movements of said electronbeam to the sound track corresponding to said pitch.

6. Apparatus for producing musical tones simulating tones of at leastone musical instrument, comprising (a) a cathode ray tube, (b) a filmsound track disposed in front of the tube face, (0) said track havingoptically recorded thereon tones from said instrument, (d) means forenergizing said tube to project at least one electron beam onto saidtube face to illuminate a spot thereon in register with said track, (e)a transducer adapted to convert light signals into electrical signals,(f) means for directing light signals from said tube passing throughsaid track onto said transducer, (g) a loudspeaker, (h) means foramplifying the electrical signals from said transducer to drive saidloudspeaker, and, (i) means responsive to a tone signal input forscanning said spot aong said track at a rate varying with the inputfrequency to thereby produce different pitched notes at saidloudspeaker.

7. Apparatus according to claim 6 including a plurality of tracksdisposed in front of the tube face, each of said tracks having opticallyrecorded thereon tones from different instruments and means connected tosaid tube for directing said beam into register with a selected one ofsaid tracks.

8. Apparatus for producing musical tones simulating tones of at leastone musical instrument, comprising (a) a film sound track havingoptically recorded thereon tones from said instrument,

(b) means for illuminating a spot in register with said track,

(c) a transducer adapted to convert light signals into electricalsignals,

((1) means for directions light signals passing through said track ontosaid transducer,

(e) a loudspeaker,

(f) means for amplifying the electrical signals from said transducer todrive said loudspeaker, and,

(g) voice operated means responsive to a variable vocal input signal forthe scanning of said spot along said track at a rate variable with saidinput signal and thereby produce tones at said loudspeakercharacteristic of said instrument.

References Cited UNITED STATES PATENTS 2,221,097 12/ 1 940 Koehl 841.182,148,166 2/1939 Kucher 84l.18 2,528,020 10/ 1950 Sunstein 841.28

H. K. SAAL BACH, Primary Examiner F. P. BUTLER, Assistant Examiner US.Cl. X.R.

